In-scope schema components -- tricky question

In the context of looking at adding an import-schema functionality to
XProc, we are of course looking at the corresponding functionality in
XSLT.

After a moderate amount of effort, I can't find the answer to the
following (closely related?) questions, starting from section 24.4.1
Validating Constructed Elements and Attributes [1], which says, _inter
alia_

  "The components in the schema constructed from the synthetic schema
   document (see 3.16 Importing Schema Components) will always be
   available for validating constructed nodes; if additional schema
   components are needed, they may be located in other ways, for
   example implicitly from knowledge of the namespace in which the
   elements and attributes appear, or using the xsi:schemaLocation
   attribute of elements within the tree being validated."

  1) Are "[t]he components in the schema constructed from the
     synthetic schema document" any different from the "in-scope
     schema components"?  I suppose not below, and call that the ISSC.

  2) Stipulate that, as allowed, when validating constructed elements,
     a schema-aware XSLT implementation does exploit some schema
     location hints as a matter of course.

      2a) If, in exploiting some hint, it encounters a definition for
          e.g. a type whose QName already occurs as the name of a type
          in the ISSC, must it throw an error?  Does it say this in
          the XSLT spec and I missed it?

      2b) Are the components it finds via hints then added to the
          ISSC?  That is, in subsequent validation of any kind, for
          example in the type signature of a function, are those
          components available?

      2c) If so, is this done lazily?  That is, if I write

           <xsl:function name="foo" as="my:hatSize">...</xsl:function>

          are there static ordering constraints wrt this declaration
          and i) xsl:import-schema or ii) validation which per (2b)
          augments the ISSC, in this case adding a definition of
          hatSize?

I realise this is seriously obscure, but we're worrying about it now
for XProc, and would rather not disagree with XSLT out of ignorance.

Thanks,

ht
-- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
                Fax: (44) 131 650-4587, e-mail: ht@inf.ed.ac.uk
                       URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Friday, 12 June 2015 15:00:58 UTC